Headlight circuit



.June 5, 1945. I G. E M GILL 2,377,706

HEADLIGHT CIRCUIT Filed April 26, 1943 ZSnventor Patented-June s. 1945 naanuon'r cracurr George E; McGill, Pontiac, main,

asslgnortoGenerai Motors Corporation, Detroit, Mich a corporation of Application April 20, ms, Serial No. seen: 1 Claims. (01. sis-as) The present invention relates to an improved headlight circuit for vehicles incorporating certain safety features and advantages which are not present in prior lighting system.

It has been the practice to protect headlight 'circuits by single overload circuit breakers with separate grounds for each headlamp so that an accidental grounding of the headlamp circuit will cause both headlamps to be extinguished. It has also been common practice to locate the dimmer or beam control switch in the positive circuit from the battery to the headlamps so that an accidental grounding of the dimmer switch will also operate the single overload circuit breaker to extinguish both headlamps.

It is an object of the present invention to provide separate circuit breakers for each headlamp and connect the ground wires from the headlamp filaments to the dimmer or beam control switch which is'grounded instead of being in the positive circuit between the battery and the headlamps.

A further object is to provide a headlight circuit with separate circuit breakers for each headlamp in which the accidental permanent grounding of the circuit to either filament of one headlamp will not affect the continued operation of the corresponding filament of the other headlam and will also cause the second filaments of both headlamps to be placed in series to operate at reduced voltage.

Further objects and advantages of the present invention will be apparent from the following description of the embodiment thereof which is illustrated in the accompanying drawing.

In the drawing, Figure l is a wiring diagram of the present circuit, and Figures 2 and 3 are similar views showing diflerent conditions in the operation thereof.

In each of the figures, the headlamps are diagrammatically shown as comprising the right hand headlamp 2 with upper beam filament I and lower beam filament I and the left hand headlamp 8 with upper beam filament II and lower beam filament II. The battery II which is grounded at II is connected on its positive side to a main lighting switch II which is shown herein as controlling only the supply of current to.

the headlight circuit. It will be understood, however, that in accordance with standard practice this switch would ordinarily also be so constructed as to control other circuits leading from the battery to auxiliary lamps such as parking and tail lamps which are not shown herein.

The switch II is movable from the open positionshown in Figure 1 to the closed position of l'iguresza'ndatocompleteacircuitfromthe battery to a wire II connected by wires 22 and II to fuses or other types of overload protection devices II and II, respectively. It willbe apparentthat. if desired, the wire II could be eliminated and wires 22 and connected directly to contacts adapted to be engaged by switch II to thereby position the respective fuses closer to the switch II. In addition to the reference-numerals heretofore mentioned as applied thereto, the respective right and left hand headlamps and fuses associated therewith may be conveniently designated and referred to as R. H. and L. H.,

From the R. H. fuse II, a wire 30 extends to one end of both the upper beam filament I and lower beam filament I of the R. H. headlamp 2. The other end of the upper beam filament I is connected by wires I2 and II to a fixed contact terminal II of a beam control switch indicated generally at II, and the other end of the lower beam filament I is connected by wires II and I2 to a fixed contact terminal II of this switch 38. From the L. H. fuse II,- a wire It extends to one end of both the upper beam filament Ill and lower beam filament of the L. H, headlamp I and the-other end of filament II is connected by wire II to wire II, while the other end of filament I2 is connected by wire II to wire I2.

'Ihe beam control switch 38 is preferably of the foot-operated type with an operating pedal or button 52 which is adapted on successive depressions to move a switch arm indicated in dotted lines at BI back and forth between the contact terminals II and II. In the present instance the switch arm BI. is grounded through the switch casing as indicated at 56. The usual'beam indicator lamp is which may be located on the vehicle instrument panel is connected by a wire 80 to the switch contact terminal II to indicate the position of the beam control switch to the operator as 'this switch completes the respective circuits to the upper and lower beam filaments as will now be described.

Referring first to Figure 1 for the normal operation of the present headlight circuit and assuming that the main switch II has been moved to its closed position, it will be seen that in the indicated position of the beam control switch 38 the upper beam filaments of both headlamps will be energized as follows: battery II, closed switch II, wire II, wire 22, R. H. fuse 26, wire Ill,

upper beam filament I of R. H. headlamp 2, wire 37,. wire II, terminal contact II, switch arm SI to ground II to energize the upper beam filament to note that the same extends through the contact terminal 44 of switch I. which is not en- 'gaged by the switch arm It in the position shown in Figure 1.

Assuming now with the main switch ll still closed that the operator epresses the beam control switch pedal '2 to ve the switch arm' from contact terminal 80 to contact terminal I,

the lower beam filaments I and I! will be energized in parallel though obvious paths which are grounded at it through the beam control switch 38. In this position of switch arm ll it will also be seen that the beam indicator lam is will not be energized but is shunted out by the grounding of contact terminal 44.

Considering now the abnormal operation of the headlight circuit described hereabove and referring first to Figure 2, there has been shown a condition in which one of the headlamp supply wires has been short circuited or grounded to blow out one of the fuses with the beam control switch it in the position shown in Figure l which normally energizes the upper beam filaments of the headlamps. In Figure 2 this short circuit has been shown as a grounding of the wire ill at 82 which has blown the 3.1!. fuse 2i and results in a deenergization of the portion of the circuit indicated in dot and dash lines which includes the upper beam filament 4 of the R. H. headlamp 2. The upper beam filament ill of the L. H. headlamp I remains energized at full strength by the circuit indicated in heavy lines, and current also flows through those portions of the circuit indicated in light lines to energize the lower beam filaments of the headlamps in series and also continue to energize the beam indicator lamp 58.

The current path for energizing the lower beam filaments may be traced as follows in Figure 2: from the positive wire 46 extending from the L. H. fuse 28 through the lower beam filament II. of the L. H. headlamp 8, wire ill, wire 40, lower beam filament 6 of the R. H. headlamp 2, and part of wire 30 to the short circuit ground 62. Current will also fiow from wire 50 through wire 42, terminal contact 44 and wire ill to the grounded beam indicator lamp it. Since the lower beam filaments are, now in series whereas they normally operate in parallel it will be apparent that such filaments receive only'one-half of the rated voltage but this has been found to cause the filaments to glow sufilciently that they can be seen for several hundred feet. Although the lower beam filament of the L. H. headlamp might possibly not be visible to an approaching driver because of the brighter intensity of the upper beam filament of this headlamp, the lower beam filament of the R. H. headlamp would be visible and thereby function as a marker for the right side of the vehicle.

A similar abnormal condition to that of Figure 2 is represented in Figure 3 in which, however, the beam control switch 38 is in the position which normally energizes the lower beam filaments of the headlamps. In this event, it will arm-roe be seen that the normal circuit for energizing the lower beam filament I! of the L. H. headlamp at full intensity will be retained while the short circuit ground 62 will cause the upper beam filaments of both headlamps to be placed in series whereby the upper beam filament I of the R. H. headlamp will serve as a marker for the right side of. the vehicle. The diagram of Figure 3 also indicates how the beam indicator lamp I} is shunted out by the beam control switch it when this switch is operated to energize the lower beam filaments.

From the foregoing it will be apparent that in the event of a short circuit and grounding of the current supply line to either filament of the R. H. headlamp, the L. H. fuse in the present circuit will not be affected and the current supply to the corresponding filament of the L. H. headlamp will be continued. At the same time the other filaments of both headlamps are placed in series to operate, at reduced voltage whereby such other filament 0f the R. H. headlamp will serve as a marker for this side of the vehicle. With the present circuit it will also be apparent that this desirable feature of the operation thereof will be obtained with the above described conditions reversed as pertains to the right and left hand headlamps in the event of a short circuit and accidental grounding of the supply line to the L. H. headlamp.

With reference to the foregoing safety feature of the present circuit it will be noted that when the fuse for one headlamp is blown the other fuse supplies current to maintain this headlamp with a dim light and that separate shorts are required to blow each fuse such as would render both headlamps inoperative. It will also be noted that since the beam control switch is grounded in the present circuit, a defective beam control switch does not blow the fuses and if this switch fails to properly ground either the upperor lower beams during normal operation, one of the contact terminals of the switch can be externally connected to ground to energize the respective upper or lower beam filaments of the headlamps.

Whereas in the present disclosure the overload circuit breakers have been referred to as fuses it should be understood that these elements may assume any desired form such as conventional bi-metallic switches or other known types of overload circuit breakers, and although the headlamp filaments have been referred to herein as upper and lower beam filaments the same may be in the nature of bright and dim filaments.

While the embodiment disclosed herein constitutes a preferred form it will also be undercluding a beam control switch interposed in connections from said respective filaments to ground. v 2. A headlight circuit including a current source, a pair of headlamps having upper beam filaments and lower beam filaments, means for connecting said current source to the filaments of said headlamps including parallel connections from the current source to the filaments of the respective headlamps, an overload circuit breaker in each of said parallel connections, and means to selectively energize the upper beam filaments or the lower beam filaments of both headlamps including a beam control switch interposed in connections from said respective filaments to ground.

3. A headlight circuit including a current source, a pair of head amps hav ng upp r beam l to one of the contact terminals of said beam filaments and lower beam filaments, and means control switch. for connecting said current source to the fila- 6. A headlight circuit including a current ments of said headlamps including a connection source, a pair of headlamps having upper beam from said current source to one end of both filafilaments and lower beam filaments, means for ments of one headlamp, an overload circuit connecting said current source to the filaments breaker interposed in said connection adjacent of said headlamps, a beam control switch havsaid current source, a parallel connection from ing a grounded switch arm and two contact said current source to one end .of both filaments terminals adapted to be selectively engaged by of the other headlamp, an overload circuit said switch arm, means connecting the upper breaker interposed in said parallel connection beam filaments of both headlamps to one of said adjacent said current source, parallel conneccontact terminals, and means connecting the tions from the opposite ends of the upper beam lower beam filaments of both headlamps to the filaments of both headlamps and from the opother contact terminal. posite ends of the lower beam filaments of both '7. A headlight circuit including a current headlamps and means to selectively connect said source, a pair of headlamps having upper beam last named parallel connections to ground. filaments and lower beam filaments, means for 4. A headlight circuit including a current connecting said current source to said filaments source, a pair of headlamps having upper beam including parallel connections from the current filaments'and lower beam filaments, and means source to the filaments of respective headlamps for connecting said current source to the filaand an overload circuit breaker in each of said ments of said headlamps including a connection connections, means to selectively energize the from said current source to one end of both upper beam filaments of both headlamps or the filaments of one headlamp, an overload circuit lower beam filaments of both headlamps in breaker interposed in said connection adjacent parallel, and means to automatically energize said current source, a parallel connection from the unselected filaments of both headlamps in said current source to one end of both filaments series upon a short circuit ground and opening of the other headlamp, an overload circuit of the circuit breaker in either of said parallel breaker interposed in said parallel connection connections causing deenergization of rthe seadjacent said current source, a beam control lected filament of one of said headlamps. switch having a grounded switch arm and two GEORGE E. McGILL.

contact terminals adapted to be selectively engaged by said switch arm, means connecting the upper beam filaments of both headlamps to one of said contact terminals, and means connecting the lower beam filaments of both headlamps to the other contact terminal.

5. The headlight circuit set forth in claim 4 with the addition thereto of a grounded beam indicator lamp, and means connecting said lamp CERTIFICATE or CORRECTION.

Patent No. 2,57? ,706.

June 5, i915.

GEORGE E. McGILL.

It is hereby certified that error appears in the printed specification of the above numbered -patent requiring correction as follows: Page 2, second column, line 71, claim 2, strike out "A headlight circuit including" and insert instead the wordssnd comma --In a grounded electrical system for headlights,-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of October, A. D. 19b5,

Leslie Frazer (Seal) First Assistant Commissioner of Patents.

from the current source to the filaments of the respective headlamps, an overload circuit breaker in each of said parallel connections, and means to selectively energize the upper beam filaments or the lower beam filaments of both headlamps including a beam control switch interposed in connections from said respective filaments to ground.

3. A headlight circuit including a current source, a pair of head amps hav ng upp r beam l to one of the contact terminals of said beam filaments and lower beam filaments, and means control switch. for connecting said current source to the fila- 6. A headlight circuit including a current ments of said headlamps including a connection source, a pair of headlamps having upper beam from said current source to one end of both filafilaments and lower beam filaments, means for ments of one headlamp, an overload circuit connecting said current source to the filaments breaker interposed in said connection adjacent of said headlamps, a beam control switch havsaid current source, a parallel connection from ing a grounded switch arm and two contact said current source to one end .of both filaments terminals adapted to be selectively engaged by of the other headlamp, an overload circuit said switch arm, means connecting the upper breaker interposed in said parallel connection beam filaments of both headlamps to one of said adjacent said current source, parallel conneccontact terminals, and means connecting the tions from the opposite ends of the upper beam lower beam filaments of both headlamps to the filaments of both headlamps and from the opother contact terminal. posite ends of the lower beam filaments of both '7. A headlight circuit including a current headlamps and means to selectively connect said source, a pair of headlamps having upper beam last named parallel connections to ground. filaments and lower beam filaments, means for 4. A headlight circuit including a current connecting said current source to said filaments source, a pair of headlamps having upper beam including parallel connections from the current filaments'and lower beam filaments, and means source to the filaments of respective headlamps for connecting said current source to the filaand an overload circuit breaker in each of said ments of said headlamps including a connection connections, means to selectively energize the from said current source to one end of both upper beam filaments of both headlamps or the filaments of one headlamp, an overload circuit lower beam filaments of both headlamps in breaker interposed in said connection adjacent parallel, and means to automatically energize said current source, a parallel connection from the unselected filaments of both headlamps in said current source to one end of both filaments series upon a short circuit ground and opening of the other headlamp, an overload circuit of the circuit breaker in either of said parallel breaker interposed in said parallel connection connections causing deenergization of rthe seadjacent said current source, a beam control lected filament of one of said headlamps. switch having a grounded switch arm and two GEORGE E. McGILL.

contact terminals adapted to be selectively engaged by said switch arm, means connecting the upper beam filaments of both headlamps to one of said contact terminals, and means connecting the lower beam filaments of both headlamps to the other contact terminal.

5. The headlight circuit set forth in claim 4 with the addition thereto of a grounded beam indicator lamp, and means connecting said lamp CERTIFICATE or CORRECTION.

Patent No. 2,57? ,706.

June 5, i915.

GEORGE E. McGILL.

It is hereby certified that error appears in the printed specification of the above numbered -patent requiring correction as follows: Page 2, second column, line 71, claim 2, strike out "A headlight circuit including" and insert instead the wordssnd comma --In a grounded electrical system for headlights,-; and that the said Letters Patent should be read with this correction therein that the same may conform to the record of the case in the Patent Office.

Signed and sealed this 9th day of October, A. D. 19b5,

Leslie Frazer (Seal) First Assistant Commissioner of Patents. 

